Chemical mechanical vapor deposition device for production of bone substitute material

ABSTRACT

A method for fabricating a substitute component for bone, including the processes of: provision of a chemical spray including at least three of calcium chloride, hydrogen phosphate, hydrogen carbonate and water to form a combined solution; reaction and precipitation of the combined solution onto a substrate; allowing the precipitated particles to form a porous structure on the substrate; applying substantially isostatic pressure to the porous structure to form a compressed structure; and (optional) providing one or more through-holes in the compressed structure to promote osteoinduction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims priorityunder 35 U.S.C. §120 to U.S. patent application Ser. No. 12/708,425,entitled Chemical Mechanical Vapor Deposition Device For Production OfBone Substitute Material, filed Feb. 18, 2010, which is a continuationapplication of and claims priority under 35 U.S.C. §120 to U.S. patentapplication Ser. No. 11/212,977, now U.S. Pat. No. 7,687,098, entitledChemical Mechanical Vapor Deposition Device for Production of BoneSubstitute Material, filed Aug. 26, 2005. Both applications are herebyincorporated by reference in their entirety as though fully set forthherein.

FIELD OF THE INVENTION

This invention relates to production of calcium phosphate mineral-basedbone substitute material using a chemical solution spray depositiondevice that accommodates porous and composite laminar structures withreinforced biocompatible polymer fibers in order to encourage new bonegrowth as well as to provide mechanical strength and rigidity comparableto natural bone.

BACKGROUND OF THE INVENTION

Bone is an organ composed of hard living tissue providing structuralsupport to the body—it serves as scaffolding. A hard matrix of calciumsalts is deposited around protein fibers. Minerals make bone rigid andprotein (collagen) provides strength and elasticity. Bone is made ofabout 70 percent mineral and 30 percent of organic matrix. In an adult,bone engages in a continuous cycle of breaking down and rebuilding. Boneabsorbing cells, called osteoclasts, break down bone and discard worncells. After a few weeks, the osteoclasts disappear, and osteoblastscome to repair the bone. During the cycle, calcium and other mineralsare withdrawn from the blood and deposited on the damaged bone surface.The outer layer of bone is called cortical bone; 80 percent of skeletalbone mass is cortical bone. Cancellous bone is an inner spongy structurethat resembles honeycomb and accounts for 20 percent of bone mass. Theshape of bone is described as long, short, flat, or irregular. The shapeis further classified as axial or appendicular. Axial bones areprotective. For example, spinal vertebrae protect the spinal cord.Appendicular bones are the limbs. Although there many shapes and sizesof skeletal bone, the bones that make up the spinal column are unique.

Cortical bone is a natural composite which exhibits a rich hierarchicalstructure. On the microstructural level are the osteons, which are largehollow fibers (about 200 microns in diameter) composed of concentriclamellae and pores. The lamellae are built from fibers, and the fiberscontain fibrils. At the ultra-structural level, the fibers are acomposite of the mineral hydroxyapatite (HAP) and the protein collagen.These specific structural features are associated with various physicalproperties. Stiffness of bone arises from the composite structure ofmineral crystals and protein fibers. Visco-elastic properties resultfrom slip at bone cement lines between osteon. The cement lines serve asweak interfaces to impart a degree of toughness to bone. As for pores,the lacunae are ellipsoidal pores, which provide space for theosteocytes, the living cells of bone. The pore structure of bone isessential in maintaining its viability and consequently its ability toadapt to mechanical stress. The processes of bone formation(osteogenesis) are involved with osteoinduction and osteoconduction.Osteoconduction is defined as the ability to stimulate the attachment,migration, and distribution of vascular and osteogenic cells within thegraft material. Osteoinduction is defined as the ability to stimulatethe proliferation and differentiation of pluripotent mesenchymal stemcells. The physical characteristics that affect the graft'sosteoconductive activity include porosity, pore size, andthree-dimensional architecture. In addition, direct biochemicalinteractions between matrix protein and cell surface receptors play amajor role in the host's response to the graft material. The ability ofa graft material to independently produce bone is termed its directosteogenic potential. To have direct osteogenic activity, the graftpreferably contains cellular components that directly induce boneformation.

Natural bone grafts have been extensively used to promote new bonegrowth (osteogenesis) in the orthopedic industry. Natural bone mineralis fundamentally a mixture of amorphous and crystalline calciumphosphate of HAP (hydroxyapatite) with Ca/P ratio of around 1.6. Naturalbone grafts are associated with problems such as limited availabilityand risky recovery procedure for the autogenous bone, and risks of viraltransmission and immune reaction for allograft bone from a cadaver.Consequently, biocompatible matrices are currently being developed tostimulate bone formation via osteoconduction and to promoteosteoinduction by using osteogenic growth factors. The biocompatiblematerial should satisfy the following: 1) incorporation and retaining ofmesenchymal cells in tissue culture, 2) rapid induction offibrilvascular invasion from the surrounding tissues, 3) havingsignificant osteoconductive properties with the host bone, 4) nosignificant immune responses, 5) biomechanical properties similar tonormal bone, 6) biodegradable properties with an absorption rateparallel to the rate of new bone deposition, and 7) sites withnoncovalently binding osteogenic biomolecules to enhance osteoinduction.Numerous polymeric systems have been studied, including poly-α-hydroxyesters, polydioxanone, propylene fumarate, poly-ethylene glycol,poly-orthoesters, polyanhydrides, etc. These systems have the advantagesof being already approved for use in humans and are available withvarying porosities in any three-dimensional shape, and have been shownto be an excellent substrate for cellular or bioactive moleculedelivery. Other types of materials include HAP (hydroxyapatite) andβ-TCP (tricalcium phosphate). They have been the two most intenselystudied materials for bone repair and regeneration. Their most uniqueproperty is chemical similarity to the mineralization phase of bone.This similarity accounts for their osteoconductive potential andexcellent biocompatibility. Both HAP and β-TCP have been shown to beexcellent carriers of osteoinduction growth factors and osteogenic cellpopulation. However, by and large, metal, ceramic or polymer materialsthat have been introduced for bone substitutes have been substantiallydenser, heavier and significantly stiffer than natural bone althoughsome ceramic materials exhibit similar chemical properties. Natural bonefails gradually when stressed under high compression. By contrast, bonesubstitute ceramic materials commonly show sudden and catastrophicfailure under compression, because most of the bone substitute materialsindividually lack the several areas of biomechanical properties ofnatural bone, such as elasticity, viscoelasticity and lamellarstructural properties.

What is needed is a calcium phosphate-based bone substitute material,and method of fabrication thereof, that is biocompatible with naturalbone, is resorbable for osteogenesis, is rigid, is elastic withreinforced biocompatible polymer fibers, is viscoelasticity through useof multi-layered laminar structures, has controlled porosity, and haspore size(s) comparable to natural bone. The bone substitute should bestrong and tough enough to support the spinal column for spinalsurgeries as well as many other orthopedic applications.

SUMMARY OF THE INVENTION

These needs are met by the invention, which provides a production deviceand manufacturing processes, for bone substitute material with excellentosteoconductive and osteoinductive characteristics, that performchemical solution spray deposition (CSSD) method incorporated with fiberreinforcing, isostatic press. The production device and manufacturingprocesses presented here rationally simulate natural bone repairing andbuilding processes under various mechanical stresses.

In order to simulate the processes of osteoblasts and osteoclasts innatural bone rebuilding or new bone formation, a chemical solution spraydeposition method is presented. In this process, solutions, whichinclude calcium and phosphate ions in separate containers, aremechanically and simultaneously sprayed into an isolated chamber withformation of significant number of small solution particles (500nanometers to 20 micro meters) in a liquid state. One container containssaturated solution of calcium chloride (CaCl₂ (aq)). The other containercontains saturated solution of hydrogen phosphate (H₃PO₄ (aq)).Optionally, a third container can be added to contain saturated solutionof hydrogen carbonate (H₂CO₃ (aq)). And finally, another container withdistilled water is added into the system to control a degree ofsaturation during the chemical reaction, i.e., high and lowsupersaturated states. It is noted that the proportion of phosphateco-precipitated depends on the temperature, pH and the concentration ofcalcium co-precipitating chemicals.

$\begin{matrix}{\frac{{mass}\mspace{14mu} {of}\mspace{14mu} {phosphorus}}{{mass}\mspace{14mu} {of}\mspace{14mu} {calcium}} = {\sigma \; A\; {h\left( {{pH},{Ca},T} \right)}}} & (1)\end{matrix}$

where σ is the maximum surface density of phosphorus, A is the surfacearea of phosphorus molecule, and the function h varies between Ca 0.1and 0.9. This relation predicts the ratio of calcium to phosphorus forchemical formation of calcium phosphates precipitation, leading to thecontrol of pH, the optimal concentration and the desirable particlesizes of each chemical during the chemical solution spray process.

The next step is that the small particles are transported into anotherisolated chamber by a reciprocating piston motion. By applyingappropriate pressure caused by the downward piston motion andtemperature to the chamber, the solution particles with calcium ioncollide with those with phosphate ion, which induces chemical reactionbetween calcium and phosphate ions in combination with water moleculesto formulate various calcium phosphate precipitates, such ashydroxyapatite (HAP), tricalcium phosphate (TCP), octacalcium phosphate(OCP), and dicalcium phosphate dihydrate (DCDP). One of the equilibriumchemical reactions is expressed as:

Ca₃(PO₄)₂(solid)

3Ca²⁺(aq)+2(PO₄)³⁻(aq)  (2)

equilibrium shift to left in presence of excessive phosphate ion.

The phosphorous contents of the minerals are very similar, and thereforeaccurate chemical analysis is required to distinguish between theseminerals from changes in the solution composition during crystal growth.At high supersaturations, it is difficult to precipitate HAP alonebecause of the spontaneous formation of precursor phases, such asamorphous DCDP, TCP and OCP. At lower supersaturations, it has beenfound possible to nucleate HAP in pH conditions where the solutions areslightly under-saturated with respect to amorphous TCP and OCP. Theshape growth curve can provide the process information of the percentagecrystalline HAP growth on the seeds through progressive amorphous andprecursor phases such as TCP, OCP and DCDP. More significantly, theratio of crystalline to amorphous structures is closely related, notonly to mechanical properties, but also to osteoconductive andosteoinductive activities during the fusion process with natural bone.The precipitates of calcium phosphate minerals in both amorphous andcrystalline structures move to a final chamber and are finally depositedon the substrate surface, preferably, calcium carbonate. They areaccumulated in thickness with the formation of porous structures. Thepore size is determined by the solution particle size during thespraying process. More significantly, the production device presentedhere enables control of various ratios of amorphous to crystallinestructures in calcium phosphate minerals by adjusting pressure,temperature, a solution particle size, concentration of chemicals andamount of solvent (distilled water), i.e., pH, based on the shape growthcurve.

For the simulation of mechanical properties of protein, which provideselastic property and strength of natural bone, biocompatible polymerfibers, preferably, PEEK (polyetheretherketone), are added to reinforcecalcium phosphate minerals during the calcium phosphate mineraldeposition. Biocompatible polymers, such as PEEK, have excellentflexural, impact and tensile characteristics. Especially, PEEK isinsoluble in all common solvents and, being crystalline, is extremelyresistant to attack by a very wide range of organic and inorganicchemicals. It has excellent hydrolysis resistance in boiling water(autoclave sterilization) and good radiation resistance (irradiationsterilization).

When a thin layer of calcium phosphate minerals fully reinforced bypolymer fibers is observed, it undergoes an isostatic press process. Theisostatic press process is used to simulate the new bone formation undervarious stresses in a human body. This process provides more compactstructures between the calcium phosphate minerals and polymer fibers;furthermore, during the process, the pore size can be controlled interms of isostatic pressure levels. The process is repeated to depositadditional thin layers until desired overall thickness is obtainedinside the production device chamber. Consequently, stiffness of bonesubstitute arises from the composite structure of calcium phosphateminerals and polymer fibers. Viscoelastic properties can be obtainedfrom slip lines between laminated thin layers of the calcium phosphateminerals.

The slip lines as weak interfaces can represent a degree of toughnessand viscoelasticity to bone substitute material. This is an advantageusing composite laminar structure. To further increase the compressivestrength and rigidity of the bone substitute, thinner calcium carbonatemineral layers, compared to calcium phosphate mineral layers, can bedeposited to simulate the natural bone cement slip lines. Also, in orderto improve osteoinductive activities, blood vessels which nourish thetissue in natural bone (i.e., Haversian canals and Volkmann's canals)are simulated by introducing a mechanical through-hole device thatallows incorporation of a finite number of through holes perpendicularor parallel to laminated directions depending on the application. Thesefeatures in combination with bone morphogenetic protein (BMP) cansignificantly increase an osteoinductive activity. Furthermore,extracellular matrix scaffolds (ECM) can be added in combination withthe polymer fibers or into transition layers (calcium carbonate layers)between the laminated calcium phosphate mineral layers. Various ECMproteins including collagen, laminin, fibronectin, andglycodaminiglcans, can be added for excellent biological scaffolds.These proteins have the advantages of supporting the migration anddifferentiation of osteoblastic progenitor cells, facilitate the bindingof growth factors responsible for osteogenesis, and resorbing within areasonably short period of time. At the cellular level, ECM moleculesexhibit a variety of activities, including acting as a substrate forcell migration, an adhesive for cell anchorage, a ligand for ions,growth factors, and other bioactive agents. ECM molecules are ideal toform layers or substrates for cell delivery to provide high localconcentrations of osteoinductive biomolecules.

The bone substitute material must have a ratio of calcium to phosphateof around 1.6 and at least 70 MPa of compressive strength with slightviscoelastic behavior. In order to further increase compressive strengthof bone substitute material, the bulk of bone substitute material canundergo an additional isostatic press process, preferably, with salinesolution. The bulk of polymer fiber reinforced calcium phosphateminerals with controlled porosity and composite laminated structures canbe fabricated for many different applications in the orthopedicindustry. For instance, the bone substitute material can be machined andfabricated for spinal fusion implants, i.e., lumbar and cervicalinter-body fusion implants. Consequently, in combination with bonemorphogenetic protein (BMP), the bone substitute implants are strong andtough enough to support spinal column with bio-safety and eventuallyfused with vertebral end bodies.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described with reference to the following figures:

FIG. 1 is a schematic diagram of a bone substitute material productiondevice.

FIG. 2 illustrates an initial vacuum process of the bone substitutematerial production device of FIG. 1.

FIG. 3 illustrates a chemical solution spray process of the device ofFIG. 1.

FIG. 4 illustrates an accelerated chemical reaction process of thedevice of FIG. 1.

FIG. 5 illustrates a chemical deposition process of the device of FIG.1.

FIG. 6 illustrates isostatic press and noble gas insertion processes ofthe production device of FIG. 1.

FIG. 7 illustrates a plastic fiber, optionally with extracellular matrixscaffold, deposition process of the device of FIG. 1.

FIG. 8 is a perspective view of a biocompatible polymer fiber.

FIGS. 9 a) and b) are respectively microscopic representations beforeand after the isostatic press process with regard to pore sizes andcompactness of a plastic fiber to calcium phosphate deposits of FIG. 6.

FIG. 10 illustrates a vacuum process of the bone substitute materialproduction device of FIG. 1 after the isostatic press processes of FIG.6.

FIG. 11 illustrates a flow chart of the overall production processes ofthe bone substitute material.

FIG. 12 illustrates a perspective view of a through-hole mechanicaldevice to simulate blood canals of natural bone.

FIG. 13 illustrates a perspective view of the through-hole mechanicaldevice of FIG. 11 with accumulated calcium based bone substitute.

FIG. 14 illustrates a perspective view of the accumulated calcium basedbone substitute separated from the through-hole device of FIG. 11.

FIG. 15 is a magnified view of section 1301 of FIG. 13.

FIG. 16 illustrates fabrication of the bone substitute material forapplications in orthopedic areas including load bearing spinal fusion.

FIG. 17 illustrates another application of the bone substitute materialin a long bone fracture.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides production of a bone substitute material usingchemical solution spray deposition (CSSD) and isostatic press processeswith reinforced plastic fibers, preferably PEEK, resulting in bonesubstitute having composite laminated structures with controlledporosity. In order to increase toughness and elastic behavior of bonesubstitute material comparable to natural bone, the composite laminarstructure is introduced with reinforced polymer fibers. In order forbone substitute material to have high compressive strength in loadbearing applications, calcium phosphate mineral is deposited and forms alayer with an option of inclusion of calcium carbonate mineral into thecalcium phosphate mineral. Another option is that calcium carbonateforms one or more separate thin layers between the calcium phosphatelayers. The high compressive strength of calcium carbonate materialcompared to calcium phosphate can provide additional rigidity of thebone substitute material. In case of any crack formed in a calciumphosphate layer, the calcium carbonate layer combined with polymerfibers can prevent micro cracks from further propagation. On the otherhand, the calcium carbonate thin layer can provide the viscoelasticproperty similar to natural bone cement in bone lamellar structures.

FIG. 1 is a schematic diagram of a bone substitute production device101. The device 101 consists of three chambers: a primary chamber 102, asecondary chamber 111 and a third chamber 115. In the primary chamber102, there are four nozzles: 1) calcium chloride solution CaCl₂ (aq)spray nozzle 104, 2) distilled water spray nozzle 105, 3) hydrogenphosphate solution H₃(PO₄) (aq) spray nozzle 106 and 4) hydrogencarbonate solution H₂CO₃ (aq) spray nozzle 107. The nozzles spraychemical solutions and distilled water with a solution particle sizeranging from 500 nanometers to 20 micrometers. Each particle size,concentration and volume inserted into the primary chamber 102 of thesolution is different and determined according to Eq. (1) to obtain theoptimal amount of the precipitates. The minimum number of nozzles foreach solution is at least one and can be higher depending on the size ofthe device 101. The primary chamber 102 includes a piston 103 with areciprocating motion and an exhaust valve 108. The downward pistonmotion 103 pushes the sprayed chemicals into the secondary chamber 111with an increase of pressure. Depending on the size of the device,multiple numbers of the secondary chambers can be incorporated into thedevice 101. Also, by the downward motion of the piston 103, the pressureis built up in the secondary chamber 111 and further increases by theclosure of a valve 112 and is monitored by a pressure gauge 109.Furthermore, heat, ranging from room temperature to 400 degree Celsius,is applied to the secondary chamber 111 and is monitored by atemperature gauge 110. When optimal values of heat and pressure areachieved inside the secondary chamber 111, the valve 112 is open torelease precipitates, obtained by chemical reactions taking place in thesecondary chamber 111, into the third chamber 115. The third chamberincludes two valves: one for noble gas insertion 113 and the other forplastic fibers or mixture of polymer fibers and extracellular matrixscaffold 114. Optionally, the valve 114 can divide into two to supplythe plastic fibers and extracellular matrix scaffold separately. Oncethe chemical precipitates are deposited on the bottom of the thirdchamber 115 or top surface of the substrate, preferable calciumcarbonate (CaCO₃), known as calcite, the pressure cover 118 is closed toapply cold gas isostatic press (room temperature) to the precipitatesthrough the valve 116. The isostatic press process is monitored by apressure gauge 117.

To present the production device 101 in further detail, the overallproduction processes can be divided into five different processes: 1)vacuum process; 2) chemical solution spray process; 3) chemical reactionprocess; 4) deposition process; and 5) substantially isostatic pressprocess. As shown in FIG. 2, when the piston 103 is at the highestreciprocating position, the valves 108, 112 and pressure cover 118 areopen while the other valves are closed. Any gas including air and smallresidual particles 201 remaining in the chambers is initially removedthrough the valve 108 using a vacuum device connected to the productiondevice 101. The vacuum process is monitored by a pressure gauge 109until the chamber achieves at least 70 to 95 percent of vacuum. Theadditional pressure gauge can be installed onto the device 101 forbetter monitoring of the vacuum process. Depending on the vacuum stateinside the chamber, the optimal amount of the chemical precipitates canbe determined.

As shown in FIG. 3, once the desirable vacuum state is achieved, thechemical solution spray process proceeds. All the valves including 108and 112 are closed. The containers of 301, 303, 304 and 302 havesolutions of Ca⁺⁺ and Cl⁻, H(PO₄)⁻, H(CO₃)⁻, and distilled water,respectively. The distilled water is sprayed into the primary chamber tocontrol the solubility of the chemicals during the chemical reactions,i.e. high saturation, low saturation and super saturation. Also, threeoptions are available in this process: (1) all the solutions with Ca⁺⁺and Cl⁻, H(PO₄)⁻, H(CO₃)⁻, are sprayed into the primary chamber 102 tohave both calcium phosphate and calcium carbonate minerals; (2) thesolutions in containers 301 and 303 are sprayed into the primary chamber102 to have calcium phosphate mineral only; and (3) the solutions incontainers 301 and 304 are sprayed into the primary chamber 102 to havecalcium carbonate mineral only. The addition of the calcium carbonatemineral increases the toughness and rigidity of the bone substitutematerial. Also, the calcium carbonate mineral serves as a growthenhancer to accelerate the formation of the calcium phosphate mineral.However, the calcium carbonate mineral exhibits poor osteoconductive andosteoinductive activities. Therefore, the ratio of calcium phosphatecompound to calcium carbonate should be carefully controlled in thisprocess.

As soon as an optimal amount of chemicals is sprayed into the primarychamber 102, the chemical reactions proceed. Each solution particlemoves freely inside the primary chamber 102 and collides with otherparticles. However, in order to accelerate the chemical reaction processand to promote highly homogenous precipitation, the piston 103 movesdownward and pushes the chemical solution particles 401 into thesecondary chamber 111, as shown in FIG. 4. Because the valve 112 isclosed, the downward piston motion creates the pressure inside thesecondary chamber 111. Further, heat is applied to the secondary chamber111, leading to rapid chemical reactions of calcium phosphate andcalcium carbonate minerals. The applied heat ranges from roomtemperature up to 400° C. The controls of pressure and temperature playimportant roles in chemical reactions of calcium phosphate and calciumcarbonate minerals. Optionally, a sensor to monitor pH level can beadded in the secondary chamber. Consequently, with a feedback controlsystem, additional calcium, phosphate, carbonate ions and distilledwater can be added to adjust pH level. When the calcium chloridesolutions reacts with the solution containing dissolved phosphate (e.g.,hydrogen phosphate), the phosphate ion is incorporated into the latticethrough surface adsorption. The surface density of co-precipitatedphosphorus is found to depend on temperature, ionic strength and pH ofthe solution. Calcium phosphate minerals are not often found in freshwater. The thermodynamically most stable form, at normal temperature andpressure is calcium hydroxyapatite (HAP), but HAP does not form readilyin spite of the occurrence of very high supersaturations. Other mineralphases such as DCPD, OCP and amorphous tricalcium phosphate (TCP,(β-TCP) form as precursor phases that transform to HAP. Severalimportant factors controlling the precipitation kinetics are: 1)thermodynamic driving force, 2) kinetics of reaction, 3) presence ofgrowth inhibitors, and 4) competing reactions. The presented productiondevice 101 includes the factors 1), 2) and 3). However, competingreactions cannot be incorporated into the device 101 because thisrequires algae formation or organic matters are involved. Therefore, theproduction device 101 can systematically provide optimal conditions forchemical reactions with regard to calcium phosphate and calciumcarbonate minerals. The optimal conditions of the chemical reactions aremonitored by the pressure 109 and temperature 110 gauges with measuringthe duration of chemical reaction. In general, when homogenousprecipitation occurs, i.e., spontaneous nucleation and growth, unstableamorphous solids or poorly crystalline HAP precede the formation ofcrystalline HAP. In condition when pH>9, amorphous calcium phosphatemineral is to convert directly into HAP.

Once the optimal conditions including the duration of chemical reactionsare met, the valve 112 and the pressure cover 118 are open and theprecipitates distribute uniformly adjacent to the bottom of the device(top surface of calcium carbonate substrate), shown in FIG. 5. The thirdchamber 115 is still in a 70-95 percent vacuum state prior to theopening of the valve 112. Further, the valve 114 is open to uniformlydistribute biocompatible polymer fibers 501 on the bottom of the thirdchamber 115, optionally, in combination with extracellular matrixscaffolds (ECM). The volumetric ratio of the polymer fibers 501 to thecalcium phosphate mineral 301 should be carefully calculated to obtainthe desirable biomechanical properties of the final product according tothe laminated theory. The significant process in this stage is thedetermination of the initial pore size. Pore size strongly depends onthe precipitate size of calcium phosphate and calcium carbonateminerals, controlled in the chemical solution spray process of FIG. 3,and volumetric ratio of amount of the precipitates and the third chamber115. Therefore, the initial pore size can be reasonably controlled withthe presented production device 101.

FIG. 6 illustrates the isostatic press process on the precipitates ofthe production device 101. After the appropriate precipitate thicknessof the bone substitute material 602 (e.g., 10-50 μm) is achieved, thepressure cover 118 is closed, and the valve 116 provides high gaspressure 603 to provide the cold gas isostatic press process. At thesame time, the valve 113 is open to insert pressurize noble gas 604,such as argon and nitrogen, to remove undesirable chemicals such ashydro-chlorine gas HCl(g), residues in solution particles of phosphateand carbonate ions 601, etc. through opened valve 112 and by opening thevalve 108 and moving the piston 103 upward. The isostatic press processis monitored by the pressure gauge 117 with the duration of the process.

A different approach from that illustrated in FIG. 5 can be made, inwhich the calcium phosphate minerals and polymer fibers, optionally withECM, are mixed prior to the isostatic press process in the productiondevice 101. As shown in FIG. 7, the polymer fibers 702 optionally withECD can be added into the third chamber separately after the isostaticpress process. The pressure cover 118 is open, and the valve 112 isclosed. It follows that the valve 114 is open to distribute the polymerfibers 702 uniformly on the top surface of the precipitates 703. At thesame time, the piston 103 is in the highest position, and the valve 108is open for all the residual and noble gases 701 to escape from theprimary and secondary chambers.

FIG. 8 shows the perspective view of the biocompatible polymer fiber801, preferably, PEEK material. The diameter 802 of the polymer fiber801 ranges from 0.001 to 0.005 inches (0.02 to 0.07 mm), and the ratioof the diameter 802 to length 803 is at least 1 to 10 or higher. Theplastic fibers should be uniformly distributed with orthotropicmechanical properties so that the directions of the plastic fibers areonly parallel to the bottom surface of the chamber or to the laminardirection.

Prior to the isostatic press process, the calcium phosphate minerals incombination with calcium carbonate are accumulated on the bottom of thethird chamber. Due to the characteristics of the chemical solution spraydeposition shown in FIGS. 3 and 5, the large pore size can be controlledand obtained. FIGS. 9( a) and 9(b) illustrate the porous structures 902and 905 near the polymer fiber 901 surrounded by the calcium phosphateor calcium carbonate minerals 904 before and after the isostatic pressprocess, respectively. Before the isostatic press process, the pore sizeis relatively large 902, and the gaps 903 between the calcium phosphateand calcium carbonate minerals 904 and the polymer fiber 901 are formedduring the chemical deposition process, shown in FIG. 9 a). However, theisostatic press process provides the reduction of pore size 905 with asignificant increase of rigidity and the excellent compactness betweenthe plastic fibers and calcium compounds. During the process, the higherthe pressure applies to the third chamber, the higher strength andrigidity the bone substitute material possesses. However, the pressureinside the chamber should be properly controlled to give the goodporosity of bone substitute material, leading to an excellentosteoconductive property. It should be noted that too much isostaticpress pressure could make the pore size too small or eliminate theporosity.

Finally, the vacuum process is repeated as shown in FIG. 10, whichillustrates use of a vacuum process in the production device 101 toremove 70 to 95 percent of gases and particles 1002 inside the chamberssimilar to FIG. 2. However, the difference is that the pressure cover112 is closed to protect the accumulated bone substitute material 1001in the third chamber. The processes continuously cycles until thedesirable thickness of the bone substitute material is obtained. Theflowchart 1101 of the overall processes of the production device isshown in FIG. 11, which illustrates the five different stages ofproduction of the bone substitute material with several options asdescribed above. Once the bulk of the bone substitute material isobtained from the production device 101, it is transferred to anotherisostatic press chamber, and optionally, an additional isostatic pressprocess can be performed applying hydrostatic pressure using salinesolution, which can be also used for cleaning and chemical disinfection.

FIG. 12 illustrates the mechanical through-hole device 1201 to createmacro size apertures of diameter 0.2-4 millimeters (preferably, 0.5-2mm) in the bone substitute material. The device 1201 consists of astainless steel plate 1202 and numerous hardened stainless steel rods1203 with dimensions of 0.5 to 2 mm in diameter and 30 to 40 mm inlength. The steel rods 1203 are uniformly distributed and attached(welded or brazed) onto the plate 1202. The mechanical through-holedevice 1201 is placed on the bottom of the third chamber in theproduction device 101. FIG. 13 illustrates the bone substitute material1301 accumulated on the mechanical through-hole device 1201. After thedesired thickness is obtained, the bone substitute material 1301 anddevice 1201 are taken out from the production device 101. It followsthat the bone substitute 1301 is separated from the device 1201. Asshown in FIG. 14, the bone substitute material block 1301 contains manyuniformly distributed through holes 1402. The through holes 1402 play avery important role in osteoinduction prior to surgeries. In combinationwith bone morphogenetic protein (BMP), the through holes increase theosteoinductive activities when bone substitute is inserted into thebody. FIG. 15 is a magnified view of section 1401 around thethrough-hole 1402 in FIG. 14. The line 1503 represents the borderlineresulting from the repeated isostatic pressed laminated layers 1501 ofthe bone substitute mineral. The polymer fibers 1502 are uniformlydistributed parallel to the laminar direction with the randomorientation on the laminate layer 1501 to provide the orthotropicmechanical property.

As shown in FIG. 16, the bulk of bone substitute material 1601 can beused in many different applications including load bearing in theorthopedic industry. The bone substitute can be crushed by a bonegrinder to produce the bone substitute powder 1603 with the size ofaround 50 to 200 micrometers for general bone healing surgeries.Furthermore, the sliced piece 1602 of the bone substitute material 1601can be fabricated for many different types of spinal implants. Spineinter-body fusion is performed from cervical, posterior, anterior ortransversely oriented positions. Cervical and posterior lumbarinter-body fusion (PLIF) involve making an incision along a center lineon the posterior side of the neck and lower back, respectively. Cervical1607 and posterior lumbar 1605 inter-body implants can be made from thepiece 1602 of the bone substitute material. Furthermore, transforaminallumbar inter-body fusion (TLIF) is an improvement of the PLIF procedurein which the spine is approached transversely or posterolaterally, froma side of a patient. ALIF refers to anterior lumbar inter-body fusion.This procedure is similar to TLIF, but is performed from the front(anterior) of the body, usually through a minimal incision in the lowerleft lower abdominal area. The ALIF 1604 and TLIF 1606 implants are alsoshown in FIG. 16. Success or failure of the surgery depends in part onwhether the insert stably remains at the location, and on whether theimplant induces new bone formation. The presented bone substitutematerial undergoes the production processes to provide thecharacteristics to be an excellent osteoconductive biocompatibiematerial such as biochemical compatibility and biomechanicalcomparability, especially load bearing applications.

In combination with BMP and ECM, the excellent osteoinduction can occurto promote new bone formation. In load bearing applications, spinalinter-body fusion between two adjacent bodies is recognized andencouraged for good biomechanical, neurophysiological and anatomicalpractices.

FIG. 17 illustrates a human femur 1701 having multiple cracks andfractures 1702. Based upon the results of computer tomography (CT)and/or magnetic resonance imaging (MRI) scan images, especially thesurface area adjacent to the damaged region 1702 of the femur 1701, thebone substitute material 1703 is fabricated with a thickness in a range3-5 mm to match and provide good contact with the damaged bone surfaceregion. The bone substitute material 1703 is tightly fixed onto thedamaged surface region using bone screws and/or other biocompatiblescrews. The bone substitute material 1703 can provide a significantincrease in osteogenesis in the damaged bone surface region, as well astemporary protection of the damaged bone over a reasonable timeinterval. Alternatively, osteogenesis activity can be promoted bywrapping the ground bone 1603 of FIG. 16 with a biocompatible membrane1704 and attaching the membrane to the damaged region, in combinationwith the BMP. FIG. 17 illustrates application of the bone substitutematerial to a long bone structure.

1. A method for fabricating a substitute component for a bone, themethod comprising: (i) providing a combined solution comprising at leasttwo of: a first aqueous solution of calcium chloride, a second aqueoussolution of hydrogen phosphate, a third aqueous solution of hydrogencarbonate and a fourth solution comprising distilled water; (ii)allowing the combined solution to form and precipitate onto a substrateat least two particles, each particle having a diameter in a rangebetween 500 nanometers (nm) and 20 micrometers (μm), and including atleast one of hydroxyapatite, tricalcium phosphate, octacalcium phosphateand dicalcium phosphate dihydrate, where the substrate has a selectedshape and is maintained in a chamber within a selected pH range andwithin a selected temperature range; (iii) allowing the depositedprecipitate particles to form a porous structure on the substrate havingdifferent selected thicknesses in at least two different regions of thesubstrate; and (iv) applying substantially isostatic pressure to theporous structure to form at least one layer of a bone component.